Printer hammer bank assembly

ABSTRACT

A hammer bank assembly useful in high-speed impact printers of the type generally employed in data processing systems. The assembly is comprised of a one-piece cast frame having openings therein to permit air cooling. A plurality of hammer modules are provided, each module including a pair of hammers resiliently mounted on a common foot member. A mounting bar having a plurality of aligned recesses is secured to the frame. Each recess is shaped so as to receive and precisely position a foot member along the length of the mounting bar. Additionally, each recess is provided with a cylindrical bore for receiving an internally threaded stud projecting from a foot member for precisely positioning the foot member in a direction perpendicular to the length of the mounting bar. Each hammer is comprised of an impact tip carried on a rigid coil structure disposed in a permanent magnet field. Energization of the coil develops a force on the coil structure to propel the hammer toward a print drum. An adjustable backstop, carrying a long wearing deformable and resilient sleeve, is provided for each hammer to establish a precise rest position.

United States Patent Helms et al.

[ Feb. 22, 1972 [54] PRINTER HAMMER BANK ASSEMBLY of Calif.

[73] Assignee: Data Products Corporation, Woodland Hills, Calif,

[22] Filed: June25, 1969 [21] Appl. No.: 844,789

Primary ExaminerWilliam B. Penn Assistant Examiner-E. M. Coven Attorney-Samuel Lindenberg and Arthur F reilich [5 7] ABSTRACT A hammer bank assembly useful in highspeed impact printers of the type generally employed in data processing systems. The assembly is comprised of a one-piece cast frame having openings therein to permit air cooling. A plurality of hammer modules are provided, each module including a pair of hammers resiliently mounted on a common foot member. A mounting bar having a plurality of aligned recesses is secured to the frame. Each recess is shaped so as to receive and precisely position a foot member along the length ofthe mounting bar. Additionally, each recess is provided with a cylindrical bore for receiving an internally threaded stud projecting from a foot member for precisely positioning the foot member in a direction perpendicular to the length of the mounting bar. Each hammer is comprised of an impact tip carried on a rigid coil structure disposed in a permanent magnet field. Energization of the coil develops a force on the coil structure to propel the hammer toward a print drum. An adjustable backstop, carrying a long wearing deformable and resilient sleeve, is provided for each hammer to establish a precise rest position.

13 Claims, 9 Drawing Figures SHEET 2 OF 4 PATENTEDFEB22 I972 3 4 W AWOQNEy PRINTER HAMMER BANK ASSEMBLY BACKGROUND OF THE INVENTION coil structure. The coil is disposed within a permanent magnet field so that when energized, a force is developed on the coil structure to rotate it from a rest position to an impact position against a character drum mounted for rotation about an axis also extending perpendicular to the plane of the coil structure.

SUMMARY OF THE INVENTION The present invention is directed to an improved hammer bank assembly useful primarily with hammers of the type generally disclosed in said US. Pat. No. 3,279,362.

More particularly, in accordance with a preferred embodiment of the present invention, a hammer bank assembly is provided comprised of a one piece cast frame having openings formed therein to permit air flow cooling. An elongated mounting bar is provided defining a plurality of truncated V- shaped recesses along the length thereof. Each recess is shaped so as to receive and precisely position a foot member of a hammer module.

In accordance with a significant aspect of the invention, each hammer module includes at least two hammers resiliently mounted on a common base or foot member receivable in one of the precisely located and shaped recesses. The use of multiple hammer modules minimizes the number of locating positions required and permits the use of larger bolts to secure the hammer module to the mounting bar, thereby facilitating the assembling of the hammer bank assembly.

t In accordance with a further aspect of the invention, the

recesses have a truncated V shape in which the angle defined between the sidewalls is slightly smaller than that defined by the corresponding walls of the foot member, thus assuring contact on both sidewalls. I

The truncated V-shaped recesses precisely locate each hammer module horizontally along the length of the mounting bar. In accordance with a further aspect of the invention, precise vertical location is achieved by fitting a stud projecting rearwardly from each foot member into a cylindrical bore of one of the mounting bar recesses. The stud is internally threaded for receiving a bolt which locks the module to the mounting bar.

In accordance with a still further aspect of the invention, a pair of backstops are provided for each hammer module, the backstops comprising threaded bolts angularly offset with respect to one another to permit the use of larger heads and sockets.

In accordance with a still further aspect of the invention, each backstop bolt has a reduced diameter front end having a deformable and resilient sleeve molded therearound. The sleeve is preferably made of a resilient material, such as vinyl, which deforms on impact to absorb energy but which subsequently recovers its original dimension so as to establish a precise hammer rest position.

In accordance with a still further aspect of the invention, each backstop is provided with a conformable insert, e.g., of vinyl, in the bolt body extending substantially perpendicular to the threads. The insert conforms to the threads in the passages of a backstop mounting bar and prevents the backstop bolt from changing position under impact.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a high speed impact printer incorporating the teachings of the present invention;

FIG. 2 is a front view, partially broken away, of a hammer bank assembly in accordance with the present invention;

FIG. 3 is a vertical sectional view taken substantially along the plane 3-3 of FIG. 2;

FIG. 4 is an enlarged side view, partially broken away, of a multiple hammer module in accordance with the present invention;

FIG. 5 is a front view of the module of FIG. 4;

FIG. 6 is a bottom view of the module of FIG. 4;

FIG. 7 is a top plan view of a portion of the hammer bank assembly in accordance with the present invention;

FIG. 8 is a rear view primarily illustrating the backstop mounting bar in accordance with the invention; and

FIG. 9 is a sectional view of a backstop in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Attention is now called to FIG. 1 which illustrates a high speed impact printer exemplary of the type generally employed for data processing applications. Briefly, theprinter of FIG. 1 is comprised of a first frame 10 supporting a hammer bank assembly 12 and a paper stepping system generally comprised of motor 14 driving tractor chains 16. The chains 16 pull edge-perforated paper 18 from a supply stack 20 past the hammer faces 22 of the hammer bank assembly 12. The printer of FIG. 1 also includes a second frame 36 which is hinged with respect to the frame 10. The frame 30 supports a movable type bearing surface such as a multitrack, drum 32 which is normally horizontally oriented and rotated about its axis by a motor 34. Means are provided for passing a printing ribbon 36 between the rotating character drum 32 and the hammer faces 22.

In the operation of the printer of FIG. I, the edge perforations of the paper 18 are engaged with the sprockets of chains 16 to thus enable the motor 14 to pull the paper past the hammer faces 22. Normally, the motor 14 steps the paper one line at a time. Printing, of course, can be accomplished only when the frame 30 is pivoted to a closed position relative to characters in front of each hammer face. By actuating a hammer at an appropriate time, the hammer face is propelled against the back side of the paper, forcing the paper against the ribbon 36 and drum 32 to thus print a character on the front side of the paper.

The prior art is replete with high-speed impact printers of the type briefly described thus far. The present invention is directed primarily to an improved hammer bank assembly 12 intended for use in a printer of the type generally depicted in FIG. 1.

Attention is now called to FIGS. 2 and 3 which respectively illustrate front and side sectional views of a hammer bank assembly 12 in accordance with the present invention.

The hammer bank assembly 12 is comprised of a one-piece cast frame 49 including first and second vertically oriented end plates 50 and 52 joined together by upper and lower L- shaped cross bars 54 and 56. Internally threaded bosses 58 and 60 respectively project upwardly and downwardly from the bars 54 and 56, as is best shown in FIG. 2.

An upper mounting bar 62 is supported on the cross bar 54 and secured thereto by bolts 64 extending through the mounting bar 62 and into threaded engagement within the threaded bosses 58. Similarly, a lower mounting bar 66 is secured to the cross bar 56 by threadedly engaging bolts extending through the mounting bar 66 into the threaded bosses 60. The bosses 58 and 60 space the mounting bars 62, 66 from the frame cross bars 54, 56 to thus permit air to flow therebetween for cooling.

The mounting bars 62 and 66 are identical and each defines a plurality of recesses 68 extending along the length thereof,

each recess projecting into the bar from a front face 69, as is best shown in FIG. 6. Each recess 68 has a truncated V shape defined by converging side walls 70 and 72 joined by a rear wall 74. Each of the recesses is precisely positioned along the length of the mounting bar so as to be able to receive and precisely horizontally locate a hammer module. More particularly, in accordance with the present invention, a plurality of multiple hammer modules are provided. In the preferred embodiment of the invention illustrated, a total of 80 hammers are provided and each hammer module includes two hammers. Thus, 40 hammer modules are required, and as will be seen hereinafter, 20 of these hammer modules are mounted on the upper mounting bar 62 and 20 are mounted on the lower mounting bar 66.

Each hammer module 78 is comprised of a common foot member 80, best illustrated in FIGS. 3 and 4 which generally includes a rear base portion 82 for locating and securing the module to a mounting bar and a forwardly projecting hammer support portion 84. The rear surfaces of the base portion 82 define a truncated V shape substantially conforming to the truncated V-shaped recesses 68 defined in the mounting bars 62 and 66. That is, the base portion 82 is provided with converging rear sidewalls 86 and 88 joined together by a rear wall 90. In order to assure contact between the walls 86 and 70 and the walls 88 and 72 when a hammer module foot member is inserted into one of the recesses, the angle between the converging walls of the foot member is made slightly larger than the angle between the converging walls 70 and 72 of the recesses. Thus, as shown in FIG. 6, the angle between the walls 86 and 88 is preferably on the order of 90.5i e and the angle between the walls 70 and 72 is 90.0:%. Both the foot members 80 and the mounting bars 62, 66 are preferably formed of plastic material having smooth surfaces to permit close contact.

By precisely locating the recesses along each of the mounting bars 62, 66, and by precisely securing each of the mounting bars to the hammer bank assembly frame cross bars 54, 56, each of the hammer modules 78 will be precisely located horizontally, or in other words along the axis of the character drum 32 of FIG. 1. In order to assure proper vertical positioning of each of the hammer modules, that is, in a direction perpendicular to the axis of the character'drum 32, a cylindrical bore 94 is provided in the rear wall 74 of each of the recesses 68. correspondingly, each of the foot members 80 is provided with an internally threaded stud 96 adapted to precisely fit into the bore 94. Preferably, the stud 96 constitutes a brass insert and the foot member 80 is formed of plastic molded around the insert. As is best shown in FIG. 3, each of the hammer modules 78 is secured in a recess 68 by a bolt 98 which extends through a cylindrical bore 94 in one of the mounting bars 62, 64 and is terminally threaded into a module stud 96. Each bolt 98 is provided with a reduced diameter portion 99 so that if too much torque is developed on the bolt in locking a hammer module into a recess, the bolt shears off instead of breaking the stud 96 out of the foot member 80. It is further pointed out that the plastic material of the foot ember 80 is very slightly resilient so as to assure positive sealing of the foot member in a recess when put under pressure.

Each of the hammer modules 78 further includes a pair of hammers, each spring mounted on the forwardly projecting portion 84 of foot member 80. As is disclosed in the aforecited U.S. Pat., each of the hammers is comprised of a rigid coil structure 100 mounted for rotation on a pair of cross-springs 102 and 104. The ends of the springs 102 and 104 remote from the coil structure 100 are secured in the portion 84 of the foot member 80. Front and rear terminal lugs 106 and 108 are electrically connected to each pair of springs 102 and 104 within the foot member portion 84. The coil structure 100 is generally comprised of a multiturn conductor coil 110 disposed within a flat rigid housing of aluminum for example. The ends of the coil 100 are electrically connected to the springs 102 and 104. An impact tip 112 is carried on the end of the rigid coil structure 100 remote from the springs 102 and 104.

As previously pointed out, half of the hammer modules are mounted with the hammers extending upwardly from the foot members secured to the lower mounting bar 64. The other half of the hammer modules are mounted in an inverted fashion from the mounting bar 62 with the coil structures depending from the foot members 80. In this manner, the front ends of all of the impact tips 1 12 lie along a common horizontal line extending parallel to the axis of the character drum 32 of FIG. 1.

In order to develop a propelling force on the coil structure to thus impact the hammer tip against the drum when the coil is energized, a magnetic field is developed extending perpendicular to the planes of the coil structures. More particularly, as is best shown in FIG. 7, a magnet piece carrier bar is provided for the lower set of hammer modules. Similarly, a carrier bar 122 is provided for the upper set of hammer modules. The carrier bars 120 and 122 are respectively secured to the lower and upper cross bars 54, 5 6 of the frame as by bolts (not shown). A plurality of pairs of magnet pieces extend from each of the carrier bars 120 and 122 so as to extend into each of the gaps defined between coil structures of adjacent hammers. As shown in FIG. 7, a plurality of first magnet pieces is secured directly to the carrier bar and each has a second magnet piece 132 secured thereto by a solid plastic adhesive 134. All of the magnet pieces 130 associated with one of the carrier bars act together to create a magnetic field extending in one direction perpendicular to the plane of the coil structures. The front magnet pieces 132 act in concert to create a field extending in the opposite direction. As a consequence of the permanent magnetic field established by the magnet pieces, energization of the coil winding 110 will develop a force in the plane of the coil structure in a direction substantially perpendicular to the axis of the character drum 32 of FIG. 1. As a consequence, the coil structure will essentially rotate about the intersection of springs 102 and 104 to impact the hammer tip 112 against the drum to thus print a character on the front surface of the paper in the manner previously set forth.

It should be recognized that if high-quality printing, in which all of the characters are printed in alignment, is to be achieved using a continually rotating drum, it is essential that all of the hammers have a precise rest position with respect to the drum and that they be precisely fired to impact against the drum when the drum is in the appropriate position. Precise vertical and horizontal location of the hammers is afforded by the previously discussed cooperation between the shape of the hammer module foot member and the mounting bar. Precise time energization of the coils is achieved by well known electronic circuitry. Still, it is essentialthat the rest position of each hammer be precisely established in order for high quality printing to be achieved. More particularly, in virtually all known impact printers, some type of adjustable backstop is provided to establish a precise rest position of each hammer. Adjustability if required to compensate for various factors which might affect the desired hammer rest position. For example, as the hammer impact tip continually rebounds from the drum against the backstop, the backstop will wear and thus it is normally necessary to periodically readjust the backstop position in order to maintain the desired rest position of the hammers. Adjustability of the backstop can also compensate for other factors such as minor variations between magnetic field strength from one gap to another.

In accordance with the present invention, a T-shaped backstop bar 138 is provided. The leg portion of the T-shaped backstop bar extends between the upper and lower frame cross bars 54 and 56 as shown in FIG. 3 with the cross portion of the backstop bar bearing against the front surfaces of the bars 54 and 56. A plurality of threaded bores are provided in the backstop bar 138, alternate bores being offset in opposite angular directions as is shown in FIG. 3. More particularly, the front ends of the backstop bores terminate along a common line immediately opposed to the rear faces of the aligned hammer impact tips of both the upper and lower sets of hammer modules. The bores however open along two spaced horizontal rows on the rear surface of the backstop bar 138, the rows being respectively disposed above and below the common line defined along the front surface of the backstop bar. By angularly offsetting alternate ones of the backstop bores, backstop bolts having larger heads can be utilized thereby facilitating easier adjustment of the backstops and minimizing the likelihood of stripping the walls of a socket extending into the bolt head.

Each backstop is comprised of a bolt 140 having a threaded shank portion 142 and a large socket head 144. The shank portion 142 is reduced at its front end 146 and additionally is provided with cutout ring portions 148. The ring portions are provided to facilitate securernent of a spongy sleeve 150, preferably molded thereon. More particularly, the sleeve 150 is preferably formed of a resilient vinyl material molded on the reduced front end 146 of the backstop bolt shank. The resilient sleeve 150 is deformable on impact and thus actual wear of either the backstop bolt or the rear surface of the hammer impact tip is minimized. The sleeve material is selected so as to easily absorb energy by deformation, but also so as to promptly regain its dimensional stability in order to establish a precise rest position of the hammers.

In order to prevent the back stop bolt from running out on impact, a recess 156 is cut in the threaded portion of the shank 142 and a vinyl insert 158 is contained therein. The insert 158 is cut by the threads of the backstop bores in bar 130 and its resiliency prevents the bolt from running out on impact.

From the foregoing, it will be recognized that an improved hammer bank assembly for use in high speed impact printers has been disclosed herein in which precise and easy positioning of the hammers is assured, thus enabling high-quality printing to be achieved.

What is claimed is:

l. A hammer bank assembly useful in high-speed impact printers, said assembly comprising:

a mounting member having a surface including a plurality of spaced recesses each including an entrance opening defined by converging side walls projecting from said surface into said member, each of said recesses further including a back wall extending between said converging sidewalls to define a truncated V shape;

plurality of hammer modules each including a foot member having a pair of sidewalls converging at substantially the same angle as said recess sidewalls and including a back wall extending therebetween to define a truncated V shape, each of said hammer modules further including at least two hammers supported on said foot member for movement with respect thereto; and

means for securing each of said hammer module foot members in a different one of said recesses with each of said foot member sidewalls contacting one of said recess sidewalls, said means for securing including means for securing said foot member back wall to said recess back wall.

2. The hammer bank assembly of claim 1 wherein said foot member sidewalls converge at a slightly greater angle than said recess sidewalls.

3. The hammer bank assembly of claim 1 including a cylindrical bore defined in each of said recess back walls and extending through said mounting member; and

an internally threaded stud fixed to said foot member and extending from the back wall thereof and receivable in said cylindrical bore.

4. The hammer bank assembly of claim 3 including a bolt extending through said cylindrical bore and terminally threaded in said stud, said bolt including a low torque resistant portion.

5. The hammer bank assembly of claim 1 wherein each of said hammers includes a flat rigid coil structure;

an impact tip carried by said rigid coil structure; and

a pair of electrically conductive spring members secured to said coil structure and said foot member for supporting said coil structure for movement with respect to said foot member. 6. The hammer bank assembly of claim 5 wherein the two hammer coil structures on each of said hammer modules extend parallel to and are spaced from one another; and

magnet means fixedly supported relative to said mounting member adapted to project into said space between the spaced coil structures of a hammer module when the hammer module is secured in one of said recesses.

7. The hammer bank assembly of claim 6 including a carrier bar fixedly supported relative to said mounting member; and wherein said magnet means includes a first permanent magnet member secured to said carried bar and a second permanent magnet member secured to said first permanent magnet member by nonmagnetic material.

8. The hammer bank assembly of claim 5 including a backstop bar fixedly supported relative to said mounting member, said backstop bar including a plurality of passages extending between front and rear surfaces thereof, said passages all opening on said front surfaces along a common line, said passages opening on said rear surface alternately along first and second lines respectively spaced above and below said front surface common line.

9. The hammer bank assembly of claim 8 including a plurality of backstop members each mounted in a different one of said backstop bar passages, each of said backstop members including a rigid shank having a front end projecting outwardly beyond said backstop bar front surface; and

a deformable and resilient sleeve secured to said backstop member front end.

10. The hammer bank assembly of claim 9 including means for varying the positioning of said backstop members in said passages for establishing the distance said backstop member front ends project beyond said backstop bar front surface.

11. An impact printer including:

1. a movable type-bearing surface;

2. a hammer bank assembly mounted adjacent to said type bearing surface, said assembly comprising:

a. a mounting member having a surface including a plurality of spaced recesses each including an entrance opening defined by converging sidewalls projecting from said surface into said member, each 'of said recesses further including a back wall extending between said converging side walls to define a truncated V shape;

b. a plurality of hammer modules each including a foot member having a pair of sidewalls converging at substantially the same angle as said recess sidewalls and including a back wall extending therebetween to define a truncated V shape, each of said hammer modules further including at least two hammers supported on said foot member for movement toward and away from said type bearing surface; and

c. means for securing each of said hammer module foot members in a different one of said recesses with each of said foot member sidewalls contacting one of said recess sidewalls, said means for securing including means for securing said foot member back wall to said recess back wall; and

3. means for moving paper between said type bearing surface and said hammers.

12. The impact printer of claim 11 including a cylindrical bore defined in each of said recess back walls and extending through said mounting member; and

an internally threaded stud fixed to said foot member and extending from the back wall thereof and receivable in said cylindrical bore.

13. The impact printer of claim 12 including a bolt extending through said cylindrical bore and terminally threaded in said stud, said bolt including a low torque resistant portion. 

1. A hammer bank assembly useful in high-speed impact printers, said assembly comprising: a mounting member having a surface including a plurality of spaced recesses each including an entrance opening defined by converging side walls projecting from said surface into said member, each of said recesses further including a back wall extending between said converging sidewalls to define a truncated ''''V'''' shape; a plurality of hammer modules each including a foot member having a pair of sidewalls converging at substantially the same angle as said recess sidewalls and including a back wall extending therebetween to define a truncated ''''V'''' shape, each of said hammer modules further including at least two hammers supported on said foot member for movement with respect thereto; and means for securing each of said hammer module foot members in a different one of said recesses with each of said foot member sidewalls contacting one of said recess sidewalls, said means for securing including means for securing said foot member back wall to said recess back wall.
 2. a hammer bank assembly mounted adjacent to said type bearing surface, said assembly comprising: a. a mounting member having a surface including a plurality of spaced recesses each including an entrance opening defined by converging sidewalls projecting from said surface into said member, each of said recesses further including a back wall extending between said converging side walls to define a truncated ''''V'''' shape; b. a plurality of hammer modules each including a foot member having a pair of sidewalls converging at substantially the same angle as said recess sidewalls and including a back wall extending therebetween to define a truncated ''''V'''' shape, each of said hammer modules further including at least two hammers supported on said foot member for movement toward and away from said type bearing surface; and c. means for securing each of said hammer module foot members in a different one of said recesses with each of said foot member sidewalls contacting one of said recess sidewalls, said means for securing including means for securing said foot member back wall to said recess back wall; and
 2. The hammer bank assembly of claim 1 wherein said foot member sidewalls converge at a slightly greater angle than said recess sidewalls.
 3. The hammer bank assembly of claim 1 including a cylindrical bore defined in each of said recess back walls and extending through said mounting member; and an internally threaded stud fixed to said foot member and extending from the back wall thereof and receivable in said cylindrical bore.
 3. means for moving paper between said type bearing surface and said hammers.
 4. The hammer bank assembly of claim 3 including a bolt extending through said cylindrical bore and terminally threaded in said stud, said bolt including a low torque resistant portion.
 5. The hammer bank assembly of claim 1 wherein each of said hammers includes a flat rigid coil structure; an impact tip carried by said rigid coil structure; and a pair of electrically conductive spring members secured to said coil structure and said foot member for supporting said coil structure for movement with respect to said foot member.
 6. The hammer bank assembly of claim 5 wherein the two hammer coil structures on each of said hammer modules extend parallel to and are spaced from one another; and magnet means fixedly supported relative to said mounting member adapted to project into said space between the spaced coil structures of a hammer module when the hammer module is secured in one of said recesses.
 7. The hammer bank assembly of claim 6 including a carrier bar fixedly supported relative to said mounting member; and wherein said magnet means includes a first permanent magnet member secured to said carried bar and a second permanent magnet member secured to said first permanent magnet member by nonmagnetic material.
 8. The hammer bank assembly of claim 5 including a backstop bar fixedly supported relative to said mounting member, said backstop bar including a plurality of passages extending between front and rear surfaces thereof, said passages all opening on said front surfaces along a common line, said passages opening on said rear surface alternately along first and second lines respectively spaced above and below said front surface common line.
 9. The hammer bank assembly of claim 8 including a plurality of backstop members each mounted in a different one of said backstop bar passages, each of said backstop members including a rigid shank having a front end projecting outwardly beyond said backstop bar front sUrface; and a deformable and resilient sleeve secured to said backstop member front end.
 10. The hammer bank assembly of claim 9 including means for varying the positioning of said backstop members in said passages for establishing the distance said backstop member front ends project beyond said backstop bar front surface.
 11. An impact printer including:
 12. The impact printer of claim 11 including a cylindrical bore defined in each of said recess back walls and extending through said mounting member; and an internally threaded stud fixed to said foot member and extending from the back wall thereof and receivable in said cylindrical bore.
 13. The impact printer of claim 12 including a bolt extending through said cylindrical bore and terminally threaded in said stud, said bolt including a low torque resistant portion. 